1. Field of the Invention
The invention relates to pipe couplings, and more particularly, to couplings of the type used to join abutting sections of pipe.
2. Description of the Prior Art
Basic couplings for joining thin walled pipe sections and thick walled pipe sections for high pressure applications, working pressures up to 100 psi, have generally proven to be unsatisfactory, since such couplings require specialized fabrication and the like. Exemplary of such problems are the myriad problems incurred with couplings for helically corrugated pipe section application.
The use of helically corrugated, spiral pipe has increased, due to the myraid new applications and modifications which have been developed. However, basic couplings for joining such pipe sections have generally proven to be unsatisfactory, with the sole exception of the coupling disclosed by U.S. Pat. No. 3,501,179, in the name of Jerald H. Boynton, et al.
In joining adjacent sections of helically corrugated, spiral pipe, the prior art has found that the corrugations of the pipe sections to be joined and the corrugations of the band-type coupling means must all be of substantially the same pitch, size and depth. Furthermore, these corrugations must be aligned so that the band can properly seat on the pipe section ends. In order to achieve this end, often one of the pipe sections must be revolved about its axis, or longitudinal movement of one pipe section with respect to the other pipe section is required. Rotational movement of one pipe with respect to the other pipe is very time consuming and not practical, or cannot be tolerated if the pipe is of large diameter or is either paved in the bottom or noncircular in cross section, such as a pipe arch. Longitudinal movement of one pipe with respect to the other pipe has also proven to be impractical because the gap between the ends of the two pipe sections could become critical as a large diameter pipe is moved longitudinally. Accordingly, the coupling must necessarily carry all of the load across the pipe.
Various prior art couplings have been utilized to join helically corrugated spiral pipe, but they have generally proven to be unsatisfactory, with the sole exception of the coupling disclosed in U.S. Pat. No. 3,501,179, which provides a pipe joint comprising a pair of substantially axially aligned, abutting lengths of butt welded, helically corrugated, spiral pipe, the abutting ends of each pipe being provided with at least one annular corrugation. The outside diameter of each annular corrugation is substantially identical with the maximum outside diameter of its helically corrugated pipe length. A coupling band encircles the adjacent ends of the lengths of pipe and means are provided for tensioning the ends of the band together. The band has a predominately flat cross section and is of a width to provide a continuous surface-to-surface seal about the entire circumference of each abutting length of pipe at at least two points thereon. The Boynton, et al, pipe joint is easily assembled without rotating one of the abutting sections, and the band may be satisfactorily positioned substantially abutting the pipe sections because the distance between the annular corrugations is constant regardless of orientation and equals the distance between deformations on the band. The annular corrugations allow more play in the pipe joint when the ends of the band are tensioned together and provide enhanced separation resistance and generally reinforce the pipe ends against damage. Such a pipe joint eliminates the myriad problems previously present in joining helically corrugated paved pipe or deformed pipe as well as the problems created by the substantial gap between the abutting ends. However, while the Boynton, et al, pipe joint proved satisfactory for most applications of helically corrugated spiral pipe, which required that the pipe be soil tight and convey water without gross leakage, i.e., that the pipe will not necessarily be water-tight but nevertheless must not permit water to leak or flow out through a joint at such a volume and velocity as to cause undue settling or erosion of the soil surrounding the pipe, it has proven unsatisfactory as a coupling to carry high pressures to be encountered in water transmission in helically corrugated spiral pipe. In fact, there are no present satisfactory uses of helically corrugated spiral pipe in high pressure applications, working pressures of up to 100 psi, because a satisfactory coupling for joining sections of butt welded, helically corrugated, spiral pipe has not been available.